Spinal fixation systems which are used to correct spinal deformities and treat spinal degenerations generally consist of a series of bone fasteners anchored in, for example, the pedicle of adjacent vertebra. The bone fasteners are interconnected to one another by one or more elongated spinal rods or plates. In order to access the spinal area for implantation of these spinal fixation systems and their individual components, open approach surgical techniques have traditionally been employed. These open procedures generally involve large skin incisions and extensive tissue retraction and resection, all which may result in considerable post-operative pain and prolonged recovery time.
More recently, surgeons have used minimally invasive techniques to reduce the post-operative effects of spinal fixation procedures. A paraspinal approach is one form of minimally invasive technique and involves muscle splitting or muscle sparing in order to gain access to the posterior elements of the spine. Such a technique minimizes trauma to tissues adjacent the spine. Unlike open approaches where muscles and other soft tissue are cut, split, stripped and dissected, the paraspinal approach involves separation or splitting of the muscles along their fibers. To perform a paraspinal surgical procedure, a midline skin incision is made and followed by bi/unilateral fascia incision. The muscles are then separated to allow access to the spine via a single skin incision. Additionally, one or more off-midline skin incisions may be made to allow for a more direct approach.
Implanting a spinal rod fixation system generally involves at least two steps: (i) placing implants (e.g., screws) into the spine and (ii) inserting a rod between the implants. The starting insertion point, the trajectory of the implants and the implants' size are important to proper implant placement. The spinal implant generally comprises a screw portion and a body portion. The screw portion is inserted into the spine and the body portion generally has a channel into which a spinal rod is inserted and secured. The procedure to insert the rod may require insertion of the rod through an incision in the skin, which may be separate and distinct from the incision through which the implant(s) is placed. In other procedures, the rod is inserted through the same incision as the implant(s).
It is desirable to have a minimally invasive spinal implant and rod introduction system which minimizes trauma to the body, enables a rod to be readily connected to multiple implants anchored at varying depths in the body, is generally simple to use and enhances direct visualization of the rod as the rod is inserted into spinal implants.